The wires that plug into these were reversed.
After I plugged them in, it still wasn't working right. The shifter wasn't going into reverse, so I had to take the whole box apart. I was afraid of what I'd find in there. I've never been one for doing electrical stuff, so imagine my relief when I opened the box and found this...
The grey lever is the shifter. The jeep has 3 settings, Low, High, and reverse. When you shift the lever, it slides over these 2 switches which change the direction and speed of the motors. So, all I had to do was flip a switch and put it all back together to cause happiness in all the land!
I love fixing things for the boys!